/**
  * Overrides SearchQueueIteratorAbstract::rewind().
  *
  * Fetches a new batch of items that are scheduled for indexing.
  *
  * @throws \RuntimeException
  *   Thrown when the collection has not been set.
  */
 public function rewind()
 {
     parent::rewind();
     $limit = $this->_agent->getLimit();
     $this->_scheduledItems = $this->_collection->fetchScheduledItems($limit);
 }